.chess {
    width: 50px;
    height: 50px;
    border: 2px solid lightgray;
    display: flex;
    box-sizing: border-box;
    justify-content: center;
    align-items: center;
    cursor: pointer;
}

.chess .chess-item {
    width: 30px;
    height: 30px;
    border-radius: 50%;
}

.chess .red{
    background: radial-gradient(#fff, #f20);
}

.chess .black{
    background: radial-gradient(#fff, #000);
}